The problem comes in and....
My parents are really against the idea of going to UCL or Warwick and wants me to go to US ( I got into really good US uni)

And would only allow me to go to UK if its like Oxbridge and Imperial (I didnt meet requirement so I didnt apply this year).

I personally LOVE England and want to study there, and although I dont meet IB qualification requirement from Oxbridge, I meet their American qualification because I self studied SAT and AP (but I have to take 2 more relevant AP exams next year)

SO My idea is that Ill reapply from UCAS in 5 months (2013 October) to either Oxford or Cambridge with totally new qualification (I can't with IB, I won't have enough points)...

I would be graduate of high school by the time of applying, and is it possible to apply with different qualification than your high school offers? Especially reapplying with different qualification?

You would have to declare all of your qualifications on your application form. So you would still have to give them your IB score, as well as the other qualification you have. They would still look at your IB scores, but if your other qualification meets their entry requirements then hopefully they will still consider your application.